harviExternal CT’s / harvi

  1. Can the CT cable be extended? Is there a max length?
  2. Will the signal from the CTs get distorted if I put them close to other CTs eg. Powerwall CT?
  3. Do I have to have a CT fitted to the solar PV feed or not?
  4. Is it better to connect PV or AC Battery to the spare CT input
  5. Why does my harvi stops transmitting when it’s dark
  6. Can I power the harvi with an external power supply?
  7. Are hardwired CT’s more accurate / update more often than a CT on a harvi?

1. Can the CT cable be extended? Is there a max length?

Yes! You can extend them up to a maximum of 100m but you MUST use a twisted pair cable (cat5). This is to maintain correct polarity throughout. Up to four CT cables can be extended using the separate twisted pairs in a CAT5 Ethernet cable.

 

2. Will the signal from the CTs get distorted if I put them close to other CTs eg. Powerwall CT?

No! The CTs can be placed in close proximity to other CTs where required 

 

3. Do I have to have a CT fitted to the solar PV feed or not?

Providing the ‘Grid’ CT is fitted then zappi/eddi will work perfectly. The solar PV CT isn’t compulsory but it will provide solar PV information on the zappi/eddi screen. This will also show on the app. 

 

4. Is it better to connect PV or AC Battery to the spare CT input

The PV CT is used only used for monitoring purposes.  Adding an AC battery CT allows you to avoid battery drain and to give the battery priority over any surplus generation (in the ECO and ECO+ modes). If you don’t want your stored energy used for heating or EV charging it is advisable to connect the CT to monitor an AC battery. 

If the harvi is only monitoring the PV it will stop transmitting at night and a red “harvi” light will show on the hub. Depending on the placement of the hub, this could be irritating to some.

 

5. Why does my harvi stops transmitting when it’s dark

harvi harvests energy from the circuit it is measuring so it doesn’t require a battery.  As a result, it will stop transmitting if there is no power flowing in the measured circuit (eg at night if measuring PV generation). 

If you have a spare grid clamp you could use this to keep harvi awake by connecting it to a spare CT input and then clamping the CT around a cable that always has power flowing through it.  Remember to set the CT Type to None if you do this. 

 

6. Can I power the harvi with an external power supply?

A 9V or 12V DC power adapter can be used in one of the CT inputs. 

 

7. Are hardwired CT’s more accurate / update more often than a CT on a harvi?

Simple answer – yes!  As harvi harvests power it transmits more when there is a high current flowing through the CT. At low power flows a hardwired CT will give a more accurate reading